按父/子 ID 重组数组。递归？

Posted 2023-05-08

【中文标题】按父/子 ID 重组数组。递归？

【英文标题】：Restructure array by parent/child IDs. Recursion?

【发布时间】：2011-04-21 16:36:08

【问题描述】：

我有一系列位置。这些位置中的每一个都可以有子位置。每个子位置也可以有子位置，依此类推：

$locations = array(
    array("id" => 1,  "parent_id" => 0, "name" => "England"),
    array("id" => 2,  "parent_id" => 0, "name" => "Scotland"),
    array("id" => 3,  "parent_id" => 0, "name" => "Ireland"),
    array("id" => 4,  "parent_id" => 0, "name" => "Wales"),
    array("id" => 5,  "parent_id" => 1, "name" => "East England"),
    array("id" => 6,  "parent_id" => 1, "name" => "London"),
    array("id" => 7,  "parent_id" => 6, "name" => "West London"),
    array("id" => 8,  "parent_id" => 6, "name" => "East London"),
    array("id" => 9,  "parent_id" => 1, "name" => "East Midlands"),
    array("id" => 10, "parent_id" => 9, "name" => "Derbyshire")
);

我想重新构造这个数组，使子数组成为父数组。像这样的东西（未经测试）：

$locations =    array("id" => 1, "parent_id" => 0, "name" => "England", "children" => array(
                    array("id" => 5,  "parent_id" => 1, "name" => "East England"),
                    array("id" => 6,  "parent_id" => 1, "name" => "London", "children" => array(
                            array("id" => 7,  "parent_id" => 6, "name" => "West London"),
                            array("id" => 8,  "parent_id" => 6, "name" => "East London")))));

这样我就可以像这样使用缩进打印出来：

LOCATIONS

England
- East England
- London
-- West London
-- East London
- East Midlands
-- Derbyshire
Scotland
Ireland
Wales

我已经尝试了几种方法，比如按父 ID 对它们进行分组，但我就是想不出这样做的逻辑，并且可能有更好的方法（也许是递归？）。

非常感谢。

【问题讨论】：

您能添加一些您尝试过的代码示例吗？顺便说一句，递归可能是通过引用将结果传递给函数的最佳方法。

【参考方案1】：

嗨，也许这会对你有所帮助，我只是为了快速将包含 parent_id 的 mysql 结果转换为可用的数据层次结构而编写它。您的输入数组也应该可以工作。这只是带有两个基本循环的几行代码。不需要递归。包括一些 cmets：

<?php

$max = count($inputArray);
$tree = array();
$flat = array();
// Create a flat hierarchy array of all entries by their id
for ($i = 0; $i < $max; $i++) 
        $n = $inputArray[$i];
        $id = $n['page_id'];
        $flat[$id] = $n;

// Then check all those entries by reference
foreach ($flat as $key => &$child) 
        // Add a children array if not already existing
        if (!isset($child['children']))
                $child['children'] = array();

        $id = $child['page_id'];
        $pid = $child['parent_id'];

        // If childs parent id is larger then zero
        if ($pid > 0) 
                // Append it by reference, which means it will reference
                // the same object across different carriers
                $flat[$pid]['children'][] = &$child;
         else 
                // Otherwise it is zero level, which initiates the tree
                $tree[$id] = &$child;
        


$tree = array_values($tree); // Indices fixed, there we go, use $tree further
?>

因此请注意 by '& reference' 字符。他们完成了所有工作，允许通过指向相同的对象从平面数组构建树。

【参考方案2】：

看到这个excellent anwser from Bill Kalwin。

还有他的presentation on "Models for hierarchical data (PHP and SQL)"

另外，您可能对storing directly data as a "nested set" structure in your DB 感兴趣。